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 * @FilePath: \briup\3-html&css\day05\7-尺寸.html
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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* .app {
            font-size: 20px;
            padding: 2em;
        } */
        .app {
            width:50%;
            font-size: 20px;
            padding: 1rem;
            background-color: lightgreen;
        }
    </style>
</head>
<body>
    <div class="app">
        mydiv
        <p class="mydiv" id="myduo" >好好学习天天向上</p>
        <br/>
        好好学习天天向上
       
    </div>
</body>
</html>